The present invention relates generally to apparatus for quantitatively measuring the power of electromagnetic radiation, and more specifically to the passive, quantitative measurement of the time-integrated power of electromagnetic radiation incident on a surface.
Exposure of humans to high-level electromagnetic fields can lead to an increase in temperature in tissue which can cause damage. There is also increasing evidence that other, more subtle effects occur at field intensities much lower than those required to produce a measurable elevation in tissue temperature. Standards for maximum human exposure to electromagnetic fields at various frequencies have been proposed, and consequently there is a need for a dosimeter which can be worn by individuals who are likely to be exposed to electromagnetic radiation.
Since it is the specific absorption rate over a known period of time that appears to be related to thermal and non-thermal biological effects, it is important that an integrating dosimeter be able to respond in a linear manner to the power density of the electromagnetic radiation incident on a surface over a wide range of field intensities. Identical information cannot be obtained by integration of the varying electric or magnetic fields, since the power density is proportional to the square of either the electric or magnetic field and the time-history of the electric or magnetic field would then be necessary to obtain a measure of the power density. Integrating personnel monitors known to the inventor are responsive to either the electric or magnetic components of the electromagnetic field except for a narrow range of field intensities, and are therefore not time-integrated power dosimeters.
For example, in U.S. Pat. No. 3,432,814 for "Electrolytic Devices," issued to T. B. Bissett on Mar. 11, 1969, the inventor describes the use of an electrochemical cell and a dipole antenna as part of a radar warning device. The system is a passive one in that no external power source is required to record the irradiation information in the electrochemical cell. However, there is no teaching therein as to how to passively measure the integrated radiation power.
Similarly, in "Radio Frequency Dosimeter," U.S. Pat. No. 3,147,439 issued to Kenneth K. Eakin on Sept. 1, 1964, the inventor teaches the use of pulse counting or charge accumulating devices to record the rectified current from an antenna receiving the incident radiation in pulsed or continuous-wave form to determine the radiation dose. Again, there is no teaching directed to the more relevant determination of the integrated power density.
The teachings of "Passive Dosimeters for Rf and Microwave Fields," by James D. Doss, Rev. Sci. Instrum. 55, 424 (1984), which contains information relevant to the subject invention, is hereby incorporated by reference herein.
Accordingly, it is an object of the present invention to provide an apparatus for passively measuring the time-integrated power of electromagnetic radiation incident on a surface.
Another object of my invention is to provide a personal dosimeter for passively determining the time-integrated power of electromagnetic radiation impinging on the body of an individual.
Yet another object of the present invention is to provide a personal dosimeter for passively determining the integrated power of electromagnetic radiation above a predetermined level impinging on the body of an individual.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.